Conventionally, when superconducting wire material is electrically connected at an intermediate connection section of a superconducting cable, an end of the superconducting wire material is cut with scissors or electrical tools at a site where the superconducting cable is laid.
For example, the superconducting wire material includes a structure in which component layers such as an intermediate layer, a superconducting layer, and a stabilizing layer are overlapped in order on a substrate of a tape shape, and depending on the situation when the superconducting wire material is cut, peeling of the superconducting layer occurred. When pieces of the superconducting wire material are connected in a state where the superconducting layer is damaged, there were cases where the superconducting layer deteriorated after executing the connection, and the superconducting performance decreased.
As a method of connection without damaging the layers composing the superconducting wire material, there is known a technique of performing treatment of an end so that the length which projects out at the end portion of the superconducting wire material is different according to each composing layer. The portions where the substrates are most projected out are overlapped and joined by depositing a superconducting thin film by vapor deposition to connect the pieces of superconducting wire material (for example, see patent document 1).